The present invention relates to technologies for growing single crystals, and in particular, to technologies for growing single crystals with desirable properties.
The fabrication of electronic devices often involve the formation of integrated circuitry on large and uniform single semiconductor crystals followed by slicing and polishing to form individual device chips. For example, power amplifiers in wireless devices such as mobile phones are first formed in a batch on a large GaAs substrate and then cut into separate dies for different wireless devices.
Typical industrial methods for growing GaAs crystals include pulling method, horizontal boat method, horizontal gradient freeze method, vertical boat method, and vertical gradient freeze method. In a crystal growth process, a raw material (e.g. a polycrystalline GaAs material) is first heated by a heater (not shown) to above its melting point. The melt is brought into contact with a seed crystal (e.g. made of GaAs), allowing the melt to crystallize from the seed crystal. An exemplified commercial crystal growth apparatus 100, shown in FIG. 1, includes an ampoule 110 that provides vacuum for crystal growth, a crucible 120 that holds the raw material 130, and heaters (not shown) around the ampoule 110 configured to melt the raw material in the crucible 120 to form a material melt 160. The crucible 120 has a seed well 140 that holds a seed crystal to start the crystal growth. A dopant source 170 can be placed in the ampoule 110 to dope substance in the crystal during its growth.
Many communication devices require integrated circuitry to be constructed on semiconductor substrates with high intrinsic resistivity in order to suppress noises in wireless communications. Traditionally, high resistivity group III-V compounds can be made by helium bombardment of low-resistivity GaAs single-crystal substrate, or doping during the growth of the crystals.
Despite the progresses made in industrial processes of growing signal crystals, there continues to be a need to simplify the manufacturing process and reduce costs, especially for growing high quality high-resistance single crystals.